Action of anaphylactic shock and anaphylatoxin on mast cells and histamine in rats.

Anaphylactic shock in rats produces disruption of mast cells. These cells are also disrupted when rat mesentery is incubated with antigen in vitro. The plasma histamine reaches a maximum about 5 min. after injection of the antigen. Though antihistamines protect rats against anaphylactic shock, they do not prevent mast cell disruption. Previous depletion by compound 48/80 of the histamine bound to the mast cells prevents anaphylactic shock and the increase in plasma histamine. Anaphylatoxin produces no mast cell alterations or plasma histamine increase, and thus does not seem to act as a histamine-releasing agent in rats. Probably nearly all the histamine liberated in anaphylaxis in rats comes from the mast cells.